Gun structure and recoil control



March 26, 1946. ca. M.. MAGRUM ETAL 2,397,188

' GUN STRUCTURE AND RECOIL CONTROL Filed Feb. 1, 1941 5 Sheets-Sheet 1 WPEI? :2

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March 26, 1946. M, MAGRUM ETAL 2,397,138

GUN STRUCTURE AND REGOIL CONTROL Filed Feb. 1, 1941 5 Sheets-Sheet 2 22 ZFEZ 2251 E 6'59 VAJE/V. /V/9 aver/N.

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March 26, 1946. G. M. MAGRUM ETAL 2,397,188

GUN STRUCTURE AND RECOIL CONTROL March 26, 194 6.

G. M. MA-GRUM ET AL GUN STRUCTURE AND RECOIL CONTROL Filed Feb. 1, 1941 5 Shets-Sheet 4 Bee/ween O'C'azwvae. M

March 26, 946- G. M. MAGRUM ET AL GUN STRUCTURE AND RECOIL CONTROL 5 Sheets-Sheet 5 Filed Feb. 1, 1941 \\\\\SIZ Patented Mar. 26, 1946 GUN STRUCTURE AND RECOIL CONTROL Gervase M. Magrum and Bernard E. OConnor, Buffalo, N. Y., assignors, by mesne assignments,

to Houdaille-Hershey Corporation,

Detroit,

Mich], a corporation of Michigan Application. February 1, 1941, Serial No. 376,950

Claims.

Our invention relates to gun structures and particularly to gun structures of the large caliber machine and rapid-firecannon type, utilized for pom-pom, firing on aeroplanes, aeroplane carriers, or other ships or craft.

The, important object. of our invention is to provide mechanical and hydraulic means coop erable to efficiently dampen and absorb the recoil and counterrecoil of such guns tothe same degree and efficiency, no matter at what elevation or depression the guns are fired, and to assure rapid but efficiently dampened return of the gunsto their firing position prior to the next firi-ng thereof.

The variou features of our invention are embodied in the structure shown on the drawings, in which, drawings:

Figure 1 is a plan view of the parts of a gun with which our invention is concerned, and showing the assembly and arrangement of the recoil controlling elements forming part of our invention;

Figure 2 is an end view of the structure shown on Figure 1;

Figure 3 is a front elevation of one end of the assembly shown in Figure 1;

Figure 4 is a plan view of one of the hydraulic cylinder structures and its controlling valve assembly;

Figure 5 is a section on plane V-V of Figure 4;

Figure 6 is a section on plane VI-VI of Figure Figure 7 is a section on plane VII-VII of Figure 2 of the recoil compensating device associated with the various valving assemblies such as shown on Figure 6;

Figure 8 is a section on plane VIII-VIII of Figure 4;

Figure 9 is a section, similar to Figure '7, but

of the counterrecoil compensating device associated with the valve assemblies shown on Figure 8; and

Figure 10 is a side elevation, on plane X-X of cradle frame l5 from which upper and lower trunnions l6 and I! extend through bearing opening I8 in the upper and lower Walls of the main cradle frame I 4. The secondary or inner cradle frame l5 supports the gun units G, of which four are shown. By swinging the trunnioned inner cradle 15, the gun assembly is moved for azimuth, and by rocking the main cradle M on its trunnion supports the gun asembly is moved for elevation firing.

Referring to Figure 3, the inner or sub-cradle I5 is subdivided by vertical walls l9 into compartments 20 in which the gun units are mounted. The walls l9 have guideways or channels 2i for receiving the guide members 22 on opposite sides of the bodies 23 of the guns so that the guns may shift longitudinally in the cradle 15 for recoil from afiring operation.

Associated with each gun unit is recoil dampening structure comprising a cylinder 24 for a piston 25 from which a piston rod 26 extends. Rigidly secured to and extending rearwardly from the inner end of each cylinder structure are supporting arms or brackets 2! which are bolted or otherwise secured to the upper wall of the sub-cradle I5. Secure on top of each gun body 23 is a coupling frame or bracket 28 whose outer end wall 29 receives and is secured to the end of the piston rod 26 of the corresponding cylinder structure 24. Thus, upon recoil movement of the gun, the piston structure will be shifted in the cylinder. The cylinder-piston structure assists in supporting the outer end of the gun body for guidance thereof during it recoil movement in the cradle Hi.

The piston rod 25 extends through and is journaled in the extension 30 on the cylinder 24 and Within the cylinder the piston rod has the diametrically enlarged portion 3! from which extends the threaded end 32 threading into the head of the piston 25 to secure this head against the enlarged portion 3|. The inner portion 25 of the piston has the axial bore 33 and the sur rounding annular channel 34 connected with the bore by passages 35. Outer and inner helical springs 36 and 31 extend between the inner end of the piston and the cylinder head 38 shown in the form of a plug threaded into the cylinder end. These springs are normally pie-compressed to hold the weight of the slidable gun structure in firing position at any elevation and to return the gun structure to firing position after each recoil.

When a gun is fired the recoil shifts the piston rearwardly in the cylinder structure against the resistance of the springs, the springs being compressed to tak up and stop the recoil movement of the piston and the sliding gun structure and then effecting the recoil movement of the piston and gun structure for return of the gun structure to firing position. To modify the operation of the springs and to assist in efiiciently damping and absorbing the recoil and counter-recoil movement of the gun slides, hydraulic means are provided for each gun unit. On top of and at the outer end of each cylinder structure is mounted a housing 39 having a cover structure 40, the housing providing a reservoir 4| for hydraulic fluid.. Each cylinder has a passageway 42 for communication cylinder in front of the piston 25, and another passageway 44 :between the reservoir and the space behind the piston 25. and B control these passageways, the valve srtuctures being similar and each comprising a valve housing 45 having a port 46, and a valve 41 within the housing normally held closed by aspring 43. j

Cooperating with each valve A is the recoil controlling valve structure R. (Figures 4 and 6),- and a counter-recoil controlling valve structure C is associated with each valv B (Figures 4 and 8). The valve structure R comprises a cylindrical housing 49 extending laterally from the cylinder 24 and below the housing 39 and may be integral with the cylinder and the housing, as shown. Secured in the inner end of the housing 49 of the valve R is a valve seat member 50 having the passageway therethrough which communicates with the passageway 52 through Valve structures A between the reservoir 4| and the space 43 in the s th cylinder wall at a point behind the piston head 25., Outwardly of the valve seat member a hollow piston 53 engages in the housing bore and has a stem 54 terminating at its outer end in the valve 55 which normally seats against the outer end of the seat member 50 to close the passageway 5|. The outer end of the housing bore is closed'by a plug 56 through which extends an adjusting member 51 threaded at its inner end to receive an abutmentmember 58 between which and the bottom of "the hollow piston a coil spring 59 is seated, this spring exerting pressure against the piston structure and tending to hold the valve 55 closed. By turning of the adjusting member 5'! for axial shift of the abutment member 58, the pressure of the spring against the valve is determined, i. e., the pressure of the spring for the desired resistance to opening of the valve 50 by pressure within the cylinder, may be determined. Between the valve seat 50 and the piston, a pas sageway 60 connects the reservoir 4| with the valve chamber. w

During recoil movement of the gun, durin which the piston 25 in the associated cylinder moves rearwardly, the valve A for the cylinder will be closed and the pressure of the fluid will be directed through the passageways 52 and 5| to the valve 55 of the recoil valve structure, and the resistance to flow past this valve is controlled by the degree of loading of the valve primarily by th spring 59. The fluid flowing past the valve 55 reaches the reservoir 4| through the passageway 65. During inward movement of the piston, the vacuum formed in the space 43 in front of the piston causes the valve structure B to open for fiow of fluid from the reservoir into the space 43. The reservoir is vented to atmosphere through the vent opening 6| in a plug 62 (Figure 5) so that a constant pressure is maintained in the reservoir, regardless of temperatures.

Referring to Figure 8, the valving arrangement within the counter-recoiling valve structure B comprises the same elements as in the valve structure. R. Primed reference numerals corresponding to the numerals of valve R will be applied to the elements in the valve structure C. The valve seat 55 has a passageway 52' communicating with the space 43 in the cylinder structure 24. During recoil movement of the gun and piston structure, the passageway 52 is .fully' exposed and then during counter-recoil moveme'ntthe fluid in front of the piston is directed through the passageway 52 against the ,valve 55, the resistance to flow being determined by the degree of loading of the valve, primarily by the spring 59. During such counter-recoil movement, the valve 13 will be closed and the valve A will be opened for flow of fluid from the reservoir 4| into thecylinder behind the piston.

For efficient and reliable operation of a gun, the resistanc to and damping of the recoil should be the same at whatever elevation angle the gun is fired. When a gun is horizontal, that is, at zero elevation, the weight of the gun slide and the piston structure to which it is secured is borne entirely by the gun carriage structure. However, when the gun is elevated, the weight of the gun slide and the piston structure is borne by the springs 36 and 31, such weight against the springs increasing as the gun elevation is increased, it being maximum at 90 elevation. Unless compensation is made for such weight differentials, the damping resistance to recoil will be decreased as the elevation increases. We have therefore provided means for automatically compensating for such weight influences on the springs 35 and 3'! in the cylinder structure.

Referring to Figures 6 and '7, elevation compensation structure D is provided in association with the recoil valve structure R. The compensation means shown comprises a cylinder 53 in which is a, piston 64 which is spring loaded by a spring 65 between the piston and an abutment head 66 at the inner end of a rod 61 extending through the bearing extension 68 of the cylinder. At the outer end of the rod 6! is a fork frame .69 journaling a roller 10 which engages in a cam slot ll of a cam plate 12 secured to the upper end of the carriage arm l0 adjacent to the supporting trunnion l3 for'the main cradle l4. The cylinder 63 is secured to the end of a bracket 13 secured to and extending from the cradle l4, as best shown on Figure 2. The arrangement of the cam slot is such that when the cradle 4 is rotated for elevation of the gun, the roller 'Hl will travel along the cam slot to shift the rod and its head 66 inwardly for compression or loading of the spring 65, the piston 64 normally resting against a stop projection 14 on the cylinder head 15. Thus, as

extending therefrom and all these pipes are connected by a common pipe 19 which in turn is connected by a pipe 80 with the chamber in the compensating element D between the piston 64 and the cylinder head 15.

A pipe 8| extends from the cylinder 63 from a point inwardly of the piston 64 to a pipe 82 from which pipe 83 extends to the reservoirs M of the respective valve structures associated with the gun units.

As the recoil compensating element D is thus connected with all of the recoil controlling valve structures R of the gun units, a description of the compensation operation for one of the gun units will apply to all of the units. Referring to Figures 6 and 7, when the gun assembly is fired, the resistance to the recoil movement is determined by the resistance pressure against the valve 55, and this resistance should be the same for all *firingangles of elevation. The opening movement of the valves 55 is resisted conjointly by the springs 59 of the valve structures R, and the spring 65 in the compensating device D. Before the valves can open, their associated pistons must overcome the resistance of the springs and force the fluid out of the chambers i1 through the piping 19 and Bi! and to the chamber 16 in the compensating device D for outward shift of the piston 64 against the resistance of the spring 65. The springs 59 are adjusted so that, when the gun assembly is at zero elevation, the conjoint resistance of the springs 59 and the compensator spring 65 will afford the desired recoil dampening. Now, if the gun assembly is elevated, and the weight of the sliding gun structure partially counteracts the force of the cylinder springs 35 and 37, the engagement of the compensating device D with the cam slot H will compress the spring 55 for the corresponding increased resistance to movement of the piston M. The loss of damping resistance of the springs 36 and 37 is thus compensated for by increased hydraulic damping resistance to the gun recoil movement, and therefore the dampening of the recoil is the same throughout the range of elevation firing from to 90.

Referring to Figure 2, the cam slot 'Il may be continued downwardly to provide for depression firing of the gun assembly. As the gun assembly is depressed, the weight of the gun slide structures will be added to the resistance of the cylinder springs 36 and 31 to gun recoil, but during such depression firing the cam structure will shift the rod 61 of the recoil compensating device outwardly to reduce the resistance of the spring 65, so that the hydraulic resistance to recoil will be lessened in proportion to the increased resistance caused by the weight of the gun slide structures. Thus through the entire range of firing of the gun assembly, the recoil resistance and dampening willremain the same.

The pressure in the outer end of the cylinder 63 of the compensating device D being connected with the reservoirs ll of the various gun units, the pressure in the outer end of the cylinder will always be that of the atmosphere. Within the chamber 16 of the device D and the spring chamhers 11 0f the valve structures R connected therewith the pressure is also atmospheric until the valves 55 are opened by the gun recoil and then the pressure is increased for movement of the compensating device piston 64, the fluid in the outer end of the cylinder 63 then flowing into the reservoirs for return of fluid to the cylinder 63 as the piston 64 assumes its normal position. The piston 64 is provided with a one-way check valve 84 through which hydraulic fluid may flow into the chamber It should the pressure in that chamber ever fall below atmospheric pressure.

Counter-recoil of the gun unit is caused by the recoil ofthe springs 36 and 31 in the cylinder 24 after recoil of the gun, and such recoil from the springs is also influenced by the elevation of the gun. and compensation should be made in order that the counter-recoil will remain the same for all elevations. This counter-recoil is controlled by the valve structures C in association with the compensating mechanism E (Figs. 8 and 9). The compensating device or structure E is shown as of the same construction and parts as the recoil compensating device D, and therefore primed reference numerals are applied on the structure E to designate the corresponding parts in the device D.

The compensating device E is located at the side of the mounting carriage structurelfl opposite to the device D, as shown on Figure 1. The cylinder 63' of the device E is supported by the bracket arm 13' extending from the outer cradle M. The roller 10' at the end of the rod 61" engages in the cam slot H of the cam plate I2 secured to the arm ID of the mounting structure, so that when the gun assembly is elevated the head 66' at the inner end of the rod 61' will be shifted for proper change in loading of the spring 65 for resisting outward shift of the piston 64' by the counter-recoil pressure in the chamber 75, ,as the counter-recoil valve structures C are operated. The spring chambers 11' of the valves C are each connected by a pipe 18' with the collecting pipe 19' which is connected by a pipe with the chamber 15' of the compensating device E. A pipe 8| connects the outer end of the cylinder 63 with the pipe 82 which is connected by the various pipes 83 with the reservoirs 4|.

After a recoil movement of the gun structure and the pistons 25, the cylinder passageways 52' will be exposed so that during the counter-recoil movement of the pistons by the springs 38 and 31, the fluid in front of the pistons will be forced through the passageways 52' against the valves 55 of the valve structures C, the pistons 53' then acting on the fluid in the chambers 11 of the valve structures C and the chamber 16' of the compensating device E for shift of the piston 64 against the resistance of the spring 65, the counter-recoil being thus hydraulically dampened.

When the guns are fired at zero inclination, the weight of the gun slider structure and the piston 25- connected thereto is not opposed to the recoil movement of the cylinder springs 36 and 31, and the springs can therefore exert their full recoil movement for returning the guns to their firing position. However, when the guns are fired at elevation, this weight of the gun is effective against the springs and opposes their recoil operation. It is therefore necessary that the hydraulic resistance against counter-recoil of the guns be lessened as the elevation increases, so as to compensate for the weight resistance against the springs and to permit the springs to function to properly restore the gun slider parts to the firing position after elevation firing.

Referring to Figures 8, 9 and 10, the cam slot H in the cam plate 12' is arranged to set the compensating device E, when the gun structure is at zero elevation, for setting of the rod 61' and its head 55' for compression and loading of the spring 65 for hydraulic resistance to operation of the valves 54 of the valve structure C, so that the springs 36 and 31 of the cylinders 24 will be dampened for proper recoil operation for return of the gun structure to firing position after firing at zero elevation. Then, as the gun structure is elevated, the cam slot H. willallow outward movement of the rod 61' in the compensating device E to correspondingly reduce the loading of the spring 55' and corresponding reduction in the hydraulic resistance of the valve structures C in proportion to and to compensate for the effect of the weight of the guns on the springs 36 and 31, so that the counter-recoil dampening will be the same for any elevation of the gun assembly, and proper return to firing position will be effected.

When the gun is fired when in depressed position, the weight of thegun parts and any resistance thereof to recoil of the springs 36, 31, is withdrawn, and the cam slot H will then set the compensator device E for increase of the hydraulic resistance suificiently so that the damping against counter-recoil will be the same as for any other position of the gun when fired.

With the structure as thus far described, the hydraulic braking or damping against recoil or counter-recoil is effective during the entire stroke of the pistons 25. It may be desirable to have the counter-recoil movement of the pistons more rapid than the recoil movement, in order to be assured that the gun, after a firing operation, will have been fully returned to firing position before a next firing.

Referring to Figures 4, and 8, a comparatively free flow passageway 85 is provided in each cylinder 24 a distance axially inwardly from its outlet passageway 52 through which the fluid is forced by thecylinder piston 25 against the loaded valve 55'. Normally, the passageway 85 is closed by the piston 25, but after a gun recoil movement this passageway 85 is exposed and is in front of the piston, so that as the piston counter-recoil movement is started by the springs 36, 37 the fluid in advance of the piston may flow comparatively freely through the passageway 85 into the reservoir 4i, and so long as the passageway remains open, the counter-recoil movement of the gun will be comparatively rapid. However, the passageway 85 is closed by the piston 25 before the piston reaches the outletpassageway 52, and then the fluid in advance of the piston can flow only by way of the passageway 52 and must open the loaded valve 55' in the valve structure C against the hydraulic resistance, and the final counter-recoil movement of the gun is thus sumciently braked and dampened so that the gun comes quietly back to its firing position.

As shown on Figure 4, the passageway 85 may be oblong and terminate at its forward end in the restricted part 85' so that the comparatively free primary counter-recoil movement is gradually restricted before the piston closes the passageway 85 and the outflow of the fluid in advance of the piston is restricted to the flow provided by the valve C.

As shown on Figure 5, the piston rod 26 of each cylinder structure 24 may be surrounded by suitable packing 86, and in advance of this packing a passageway 81 will return to the reservoir 4| any fluid which might have been forced out between the piston rod and its bearing structure 30.

We have thus provided, for a gun structure of the type referred to, practical and efficient means for damping and braking the recoil and the counter-recoil of the gun to th same degree for any elevation of the gun and for assuring efficient return of the gun to firing position prior to the next firing thereof. The compensation for effective change in weight due to elevation or depression is accomplished entirely automatically 1 7 met es.

andaccurately, so that the gun operation is at the same efliciency for any firing elevation.

Our improved combined mechanical and hydraulic control for absorbing recoil and counter.- recoil forces will permit the use of a lighter mounting frame or carriage for the gun. As our improved control means functions uniformly throughout the range of firing positions, increased accuracy of firing is assured. Accurate setting of the control system can be readily accomplished by the externally adjustable means provided for the recoil and counter-recoilvalve structures R and C.

. We haveshown a practical and eflicient embodiment of the features of our invention but we do not desire to be limited to the exact construction and arrangement shown and described, as changes and modifications may be made without departing from the scope of the invention.

7 We claim as follows: a

1. A gun structure of the class described comprising a mounting carriage, a gun slide movable on said carriage in response to firing recoil, a control device paralleling said gun slide and comprising a cylinder element secured to the carriage and a piston element connected to follow the recoil movement of said gun slide, a spring in said cylinder for-resisting movement of said piston on recoil and for moving said piston and said gun slide back into firing position after recoil, a reservoir on said cylinder element for providing hydraulic fluid for said cylinder and for receiving the fluid displaced by movement of the piston therein, a valve for controlling the displaced fluid flow during gun recoil, spring means for resisting opening of said valve, a chamber behind said valve for receiving hydraulic fluid under pressure, compensating means comprising a cylinder and a plunger therein and a loading spring for the plunger, a connection between said compensating means cylinder and said chamber behind said valve, said compensating means cylinder and said connection and said chamber containing hydraulic fluid subjected to pressure by said spring loaded plunger for cooperating with said spring means to resist the opening of said valve, means mounting said compensating means cylinder to follow the elevation movement of the gun slide, cam means connecting said compensating means loading spring with the gun mounting carriage, said cam means during zero elevation of the gun actuating said loading spring for loading of said plunger for maintaining normal hydraulic resistance in the chamber behind said valve for assisting said valve in resisting the displaced fluid flow during gun recoil, said cam mechanism being effective during elevation of the gun to increase the loading of said loading spring and plunger for increasing the hydraulic resistance in said chamber to movement of said valve dampening of the recoil will be the same for any angle of firing elevation.

2. Recoilcontrol fora gun mounted in a cradle trunnioned on a mounting frame, comprising a' recoil cylinder mounted on the cradle, a piston in said cylinder connected to .follow the recoil movement of the gun, spring means in said cylinder for resisting movement of said piston on recoil and for moving said gun back to firing position, a reservoir on said cylinder for providing hydraulic fluid for said cylinder and for receiving the fluid displaced by the recoil movement, a valve for controlling the displaced fluid flowduring gun recoil, a chamber behind said valve for hydraulic fluid for resisting opening of the valve, a compensating cylinder connected with said chamber, a plunger in said compensating cylinder and a loading spring therefor whereby said fluid in said compensating cylinder and said chamber will be subjected to pressure for resisting opening of said valve, said compensating cylinder being mounted to follow the elevation movement of said gun, an abutment head in said compensating cylinder for the spring therein and a rod extending therefrom, and cam means connecting the end of said rod with said mounting frame, said cam means being effective upon swing of the gun above zero elevation to shift said rod for corresponding increase in loading of said compensating cylinder spring and plunger for increasing the'hydraulic resistance in said chamber to opening movement of said valve in accordance with the increasing weight of the gun against the spring means in said cylinder whereby to effect the same recoil damping during all firing elevations above zero.

3. Recoil control for a gun mounted in a cradle trunnioned on a mounting frame, comprising a main cylinder extending parallel with the gun and supported from the cradle, a piston in said cylinder connected to follow the recoil movement of the gun, spring means in said cylinder resisting the movement of said piston by the gun recoil, a reservoir on said cylinder for providing bydraulic fluid therefor and for receiving the fluid displaced by movement of said piston, a valve for controlling the displaced fluid flow during gun recoil, a spring resisting open movement of said valve, a chamber behind said valve for fluid under pressure for assisting said spring in resisting opening of said valve, a compensating cylinder connected with said chamber, a plunger in said compensating cylinder adapted to be shifted by the hydraulic fluid displaced upon opening movement of said valve, a loading spring for said plunger, an abutment for said loading spring, means mounting said compensating cylinder to follow the elevation movement of said gun, and cam means connecting said abutment with said mounting frame, said cam mechanism being effective when the gun is at zero elevation to effect loading of said plunger for predetermined hydraulic resistance to the opening of said valve, and being effective during elevation of the gun above zero to increase the loading of said plunger by said spring for a corresponding increase in hydraulic resistance to opening of said valve whereby to maintain such predetermined hydraulic resistance during any angle of elevation of the gun above zero.

4. Recoil control for a gun mounted in a cradle trunnioned on a mounting frame, comprising a main cylinder extending parallel with the gun and supported by said cradle, a piston in said cylinder connected to follow the recoil and counter-recoil movement of the gun, spring means within said cylinder for resisting the recoil movement and for moving the piston and gun back to firing position after recoil, a reservoir on said cylinder for hydraulic fluid for the cylinder and for receiving the fluid displaced by the movements of the piston, a valve for controlling the recoil flow, a chamber behind said valve for hydraulic fluid under pressure for resisting opening movement of the valve, a recoil compensating cylinder connected with said chamber, a plunger in said recoil compensating cylinder and a loading spring for holding said plunger for compression of the fluid in said chamber, an abutment for said loading spring, said recoil compensating cylinder being mounted to follow the elevation movement of the gun, cam means connecting said abutment with said mounting frame, said cam means being effective at zero gun elevation to hold said abutment for spring loading of said plunger for a predetermined pressure in said chamber for resisting opening of said valve and being effective to increase the spring loading of said plunger during elevation of the gun above Zero for maintaining such predetermined resistance, a second valve for controlling the displaced fluid during counter-recoil of the gun by the spring means in said main cylinder, a chamber behind said second valve for hydraulic fluid under pressure for resisting opening of the valve, a counter-recoil cylinder connected with said chamber behind said second valve, a plunger in said counter-recoil cylinder and a loading spring therefor, an abutment for the loading spring in said counter-recoil cylinder, said counter-recoil cylinder being connected to follow the elevation movement of the gun, and cam means connecting the abutment in said cylinder with said mounting frame, said cam means for said counter-recoil cylinder being effective when the gun is at zero elevation to load the plunger in said cylinder for hydraulic pressure in the chamber behind said second valve for corresponding resistance to opening of said valve, and being effective during elevation of the gun to decrease the loading of said plunger whereby to maintain said predetermined counter-recoil resistance.

5. Recoil control for a gun mounted in a cradle trunnioned on a mounting frame, comprising a recoil cylinder extending parallel with the gun and supported on said cradle, a piston in said cylinder connected to follow the recoil movement of the gun, spring means in said cylinder resisting the recoil movement of said piston, a reservoir on said cylinder for providing hydraulic fluid therefor and for receiving the fluid displaced by recoil movement of the piston, a valve for controlling the displaced fluid flow during gun recoil, a chamber behind said valve for hydraulic fluid under pressure for resisting opening of the valve, a recoil compensating cylinder having a plunger therein and a loading spring therefor, a connection between said chamber and said compensating cylinder for the fluid displaced by said valve when opening whereby said plunger will be moved against the resistance of said loading spring, means supporting said compensating cylinder to follow the gun elevation movement, an abutment for said loading spring and a rod extending therefrom, a plate on said mounting frame having a cam slot therein, the end of said rod engaging in said cam slot, said cam connection being effective during zero elevation of the gun to hold said loading spring for loading of said plunger for predetermined resistance against opening of said valve and being effective during elevation of the gun above zero for increasing the loading of the plunger for corresponding increase in the hydraulic resistance to opening of the valve whereby such predetermined resistance of valve movement and consequently gun recoil will be maintained for any angle of elevation of the gun above zero.

GERVASE MI. MAGRUM. BERNARD E. OCONNOR. 

